The ExtremeXOS software provides examination and replacement services for the EXP field.
These services behave like the dot1p QoS (Quality of Service) commands. When EXP examination is enabled, the EXP value from the received frame is used to assign the packet to a QoS profile. Once a packet is assigned to a QoS profile, the EXP value may be overwritten in hardware before being transmitted. By default, the QoS profile EXP value is equivalent to the QoS profile number one (QP1). To enable QoS for MPLS (Multiprotocol Label Switching) LSPs, use the following command: enable mpls exp examination
This command enables EXP examination for MPLS received packets. When EXP examination is enabled, the EXP field in the outer or top label of the label stack is used to assign the received packet to an internal switch qosprofile. If enabled, all MPLS packets are mapped to a qosprofile based on the configured EXP bit value. That is, a packet with an EXP value of 0 is mapped to qosprofile QP1, a packet with an EXP value of 1 is mapped to qosprofile QP2, and so on. By default, EXP examination is disabled and all received MPLS packets are sent to QP1.
Each EXP value can be assigned a qosprofile. Multiple EXP values can be assigned to the same qosprofile. The following command is used to configure the switch to route packets with a received EXP value to a specific qosprofile:
configure mpls exp examination {value} value {qosprofile} qosprofile
The switch can overwrite the EXP value in the outer label of an MPLS packet.
The following command is used to enable the switch to replace the EXP value:
enable mpls exp replacement
This command enables EXP replacement for MPLS transmitted packets. When EXP replacement is enabled, the EXP field in the outer or top label of the label stack is replaced with the EXP value configured for the QoS profile for which the packet was assigned. By default, EXP replacement is disabled and packets are propagated without modifying the EXP field value.
Each qosprofile can be assigned an EXP value used to overwrite the EXP bit field in the outer label of the transmitted packet.
All qosprofiles can be configured to overwrite the EXP bit field using the same EXP value. The following command is used to configure the switch to overwrite MPLS packets transmitted from a specific qosprofile with a new EXP value:
configure mpls exp replacement {qosprofile} qosprofile {value} value
Note
On the X670-G2 and X770, when exp examination is enabled, the dot1p value of VPLS/VPWS terminated frames are set from the internal priority. The enable/disable dot1p replacement commands do not have any effect in this situation. A future release will eliminate this restriction.
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